Catalytic partial oxidation process using a catalyst system having an upstream and a downstream part

ABSTRACT

The invention relates to a process for the catalytic partial oxidation of a hydrocarbonaceous feedstock, wherein a feed mixture having the hydrocarbonaceous feedstock and a molecular-oxygen containing gas is contacted with a catalyst system having an upstream part and a downstream part, the downstream part being in the form of a porous catalyst bed, wherein the catalyst system is retained in a reactor, the reactor having an upstream part that contains the upstream part of the catalyst system and a downstream part that contains the downstream part of the catalyst system, wherein the upstream part of the catalyst system only partly fills the cross-sectional area of the fluid flow path of the upstream part of the reactor and the downstream part of the catalyst system completely fills the cross-sectional area of the fluid flow path of the downstream part of the reactor. The invention further relates to a reactor having such a catalyst system and a catalytic reaction zone for the water-gas shift conversion of the effluent of the catalyst system, to a fuel cell system having such a reactor and a fuel cell, and to a vehicle provided with such a fuel cell system.

FIELD OF THE INVENTION

The present invention relates to a process for the catalytic partialoxidation of a hydrocarbonaceous feedstock, wherein a feed mixturecomprising the hydrocarbonaceous feedstock and a molecular-oxygencontaining gas is contacted with a catalyst system having an upstreampart and a downstream part, to a reactor comprising such a catalystsystem and a catalytic reaction zone for the water-gas shift conversionof the effluent of the catalyst system, to a fuel cell system comprisingsuch a reactor and a fuel cell, and to a vehicle provided with such afuel cell system.

BACKGROUND OF THE INVENTION

Partial oxidation of a hydrocarbonaceous feedstock, in particularhydrocarbons, in the presence of a catalyst is an attractive route forthe preparation of mixtures of carbon monoxide and hydrogen, normallyreferred to as synthesis gas. The partial oxidation of hydrocarbons isan exothermic reaction represented by the equation:C_(n)H_(2n+2)+n/2O₂→n CO+(n+1)H₂

There is literature in abundance on the catalysts and the processconditions for the catalytic partial oxidation of hydrocarbons.Reference is made, for instance, to EP-A-303 438, U.S. Pat. No.5,149,464, EP-B-576 096, WO 99/37380, and WO 99/19249.

In a catalytic partial oxidation process in a fixed catalyst bed, thetemperature of the top layer, i.e. the layer at the upstream end of thecatalyst bed, is typically higher than the temperature furtherdownstream in the catalyst bed. This is due to the fact that thecatalytic partial oxidation reaction is mass and heat transfer limited,i.e. full conversion is subject to mass and heat transfer limitationsbetween the bulk of the gaseous feed mixture and the catalyst surface,and/or that some endothermic reforming reactions might occur in thedownstream part of the catalyst bed.

High temperatures in the top layer of the catalyst are unwanted, sincethe rate of catalyst deactivation increases with temperature. Therefore,there is a need in the art for a catalytic partial oxidation processwherein the temperature in the top layer of the catalyst bed can bereduced.

In International Patent Application WO 01/46068, it was found that, in aprocess for the catalytic partial oxidation of a hydrocarbonaceousfeedstock using a fixed bed catalyst, the temperature of the upstreampart of the catalyst can be reduced by carrying out the process in areactor retaining the fixed bed catalyst, which reactor is designed suchthat a part of the conversion product flows back to the zone justupstream of the catalyst bed.

SUMMARY OF THE INVENTION

It has now been found that, in a catalytic partial oxidation process,very high temperatures at the upstream surface of the catalyst can beavoided by using a catalyst system having an upstream part wherein partof the feedstock is converted and a downstream part, wherein theconversion is substantially completed, wherein the upstream part of thecatalyst system only fills part of the cross-sectional area of the flowpath of the feed mixture.

Accordingly, the present invention relates to a process for thecatalytic partial oxidation of a hydrocarbonaceous feedstock, wherein afeed mixture comprising the hydrocarbonaceous feedstock and amolecular-oxygen containing gas is contacted with a catalyst systemhaving an upstream part and a downstream part, the downstream part beingin the form of a porous catalyst bed, wherein the catalyst system isretained in a reactor, the reactor comprising an upstream part thatcontains the upstream part of the catalyst system and a downstream partthat contains the downstream part of the catalyst system, wherein theupstream part of the catalyst system only partly fills thecross-sectional area of the fluid flow path of the upstream part of thereactor and the downstream part of the catalyst system completely fillsthe cross-sectional area of the fluid flow path of the downstream partof the reactor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a longitudinal section of one embodiment ofa catalyst system that can suitably be used in the process according tothe invention.

FIG. 2 shows a longitudinal section of a part of a reactor containingthe catalyst system of FIG. 1.

FIG. 3 shows a longitudinal section of a part of another embodiment of areactor that can suitably be used in the process according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference herein to the cross-sectional area of the fluid flow path isto the cross-sectional area perpendicular to the overall flow directionof the fluid. The overall fluid flow direction in the upstream part ofthe reactor may be different from the fluid flow direction in thedownstream part of the reactor. Reference herein to completely fillingthe cross-sectional area means that the catalyst bed, i.e. thehoneycomb, foam, wire arrangement, packed bed or the like, completelyfills the cross-sectional area. The catalyst bed as such of thedownstream part of the catalyst system is porous and thus has, bydefinition, open area. This open area is not to be taken into accountfor determining whether the catalyst bed completely fills thecross-sectional area of the fluid flow path.

Since the cross-sectional area of the fluid flow path in the upstreampart of the reactor is only partly filled with catalyst, part of thereactants can pass the catalyst without being contacted with thecatalyst. In the downstream part of the reactor, the fluid flow path iscompletely filled with catalysts and the reactants are forced to contactthe catalyst.

In the process according to the invention, part of the feedstock isconverted at the upstream part of the catalyst system before thepartially converted feedstock is contacted with the downstream part ofthe catalyst system. Preferably 5 to 75% (v/v) of the feedstock isconverted at the upstream part of the catalyst system, more preferably10 to 50% (v/v), even more preferably 15 to 40% (v/v).

Preferably, the upstream part of the catalyst system is smaller involume than the downstream part of the catalyst system. More preferably,the volume of the upstream part is at most a fifth of the volume of thedownstream part, even more preferably at most a tenth, most preferablyat most a twentieth. Reference herein to volume is to the volume of thecatalyst bed or arrangement including its pores.

As has been described hereinbefore, very high temperatures at theupstream surface of the downstream part of the catalyst system can beavoided in the process according to the invention. Without being boundto any theory, it is believed that the presence of conversion productsin the fluids contacting the downstream part of the catalyst causes areduction of the temperature prevailing at the upstream surface of thedownstream part of the catalyst system.

Preferably, the temperature of the upstream surface of the downstreampart of the catalyst system is at most 1150° C., more preferably at most1100° C.

It has been found that the temperature of the upstream surface of thedownstream part of the catalyst system can be further reduced if the(partly converted) feed mixture that contacts the upstream surface ofthe downstream part has a component of its flow direction that isparallel to the upstream surface of the downstream part of the catalystsystem, such as described in International Patent Application WO01/46068 herein incorporated by reference. This is for example the casewhen the feed mixture is approaching the downstream part of the catalystin a swirling movement.

It has been found that, in the process according to the invention, thetemperature at the upstream surface of the downstream part of thecatalyst system is in general lower than the temperature at the upstreamsurface of the upstream part of the catalyst system. It will beappreciated that it will inter alia depend on the relative volumes andamounts of catalytic active material of the upstream and downstreamcatalyst parts and of the exact configuration of those parts, if and towhat extent the temperature at the upstream surface of the downstreampart is lower. The temperature of the upstream surface of the downstreampart of the catalyst system is preferably at least 50° C. lower than thetemperature of the upstream part of the catalyst system.

In order to achieve a high yield in the process according to theinvention, it is important that the degree of feedstock conversion andthe selectivity towards carbon monoxide and hydrogen of the downstreampart of the catalyst system are high. This can be achieved by using adownstream part in the form of a porous catalyst bed, since a porouscatalyst has a relatively high specific surface area. Suitable porouscatalyst beds comprise a porous, fixed arrangement of catalyst carrierprovided with a catalytically active material. Suitable porous, fixedarrangements of catalyst carrier are known in the art. Examples are apacked bed of catalyst carrier particles, a ceramic or metal monolithicstructure such as a foam or a honeycomb, an arrangement of metal gauzesor wires or combinations thereof.

Since only part of the feedstock needs to be converted at the upstreampart of the catalyst system, only part of the feedstock needs to becontacted with the upstream part of the catalyst system. By arrangingthe upstream part of the catalyst system in the reactor in such way thatit only partly fills the cross-sectional area of the fluid flow path,part of the feedstock will by-pass the upstream part of the catalyst,thereby minimising the pressure drop over the upstream part of thecatalyst system.

Another consequence of the fact that only part of the feedstock needs tobe converted at the upstream part of the catalyst system is that theupstream part does not need to have a relatively high specific surface.Therefore, the upstream part of the catalyst may be in the form of anon-porous fixed arrangement. Suitably, the upstream part of thecatalyst system is in the form of a porous or non-porous fixedarrangement of catalyst carrier provided with catalytically activematerial.

Since the upstream part of a catalyst is the part that will be mostsubjected to thermal shocks, the catalyst carrier of the upstream partof the catalyst is preferably made of metal.

Preferably, such a metal catalyst carrier is in the form of a non-porousmetal structure, for example a metal foil or plate. Typically such metalfoils or plates will have a thickness in the range of from 0.1 to 2 mm.A non-porous metal structure can be made of more robust material, i.e.more resistant to high temperatures and high thermal shocks, than porousmetal arrangements such as foams or arrangements of metal wires. Thus,by using a non-porous metal structure as the catalyst carrier of theupstream part of the catalyst system, the catalyst system is most robustat the point where the conditions, especially temperature and thermalshocks, are most severe.

Reference herein to conversion is to the percentage of thehydrocarbonaceous feedstock that is converted into lowerhydrocarbonaceous compounds and/or carbon oxides. Reference herein toselectivity is to the sum of moles carbon monoxide and hydrogen produceddivided by the theoretical maximum sum of moles carbon monoxide andhydrogen that can be produced. Reference herein to a porous catalyst isto a catalyst having pores, i.e. spaces or interstices between adjacentportions of the catalyst, having an average diameter in the order ofmagnitude of 0.05 to about 3 mm. These pores are to be contrasted withpores which may be present in the catalyst material itself, typicallyhaving an average diameter in the order of magnitude of tenths to a fewmicrometers. Examples of porous structures are foams, honeycombs, wirearrangements and packed beds of particles.

Suitable catalyst carrier materials, both for the upstream and thedownstream part of the catalyst system, are well known in the art andinclude refractory oxides, such as silica, alumina, titania, zirconiaand mixtures thereof, and metals. Preferred refractory oxides arezirconia-based, more preferably comprising at least 70% by weightzirconia, for example selected from known forms of (partially)stabilised zirconia or substantially pure zirconia. Most preferredzirconia-based materials comprise zirconia stabilised orpartially-stabilised by one or more oxides of Mg, Ca, Al, Y, La or Ce.Preferred metals are alloys, more preferably alloys containing iron,chromium and aluminium, such as fecralloy-type materials.

Metal catalyst carriers are preferably coated with a stabilised orpartially stabilised zirconia. The zirconia layer is coated on thecatalyst carrier prior to applying the catalytically active metal(s) onit. Advantages of such a coating are that the stability and the yield ofthe catalyst are improved and that direct contact between thecatalytically active material and the metals from the metal carrier isminimised or avoided.

The stabilised or partially stabilised zirconia may be coated on thecatalyst carrier by techniques known in the art, preferably by means ofwashcoating techniques such as spraying, dipping or direct applicationof a sol or suspension of zirconia. Preferably, the carrier is dried andcalcined after washcoating. The sol or suspension of zirconia maycomprise small amount of other oxides or binders, for example alumina.Preferably, the amount of other oxides or binders is less than 20% byweight, based on the amount of stabilised zirconia, more preferably lessthan 10% by weight.

Preferably, the zirconia is stabilised with one or more oxides selectedfrom oxides of Ca, Mg, Al, Ce, La, and Y, more preferably selected fromCa and Y. Preferably, the amount of stabiliser is in the range of from 1to 10% by weight, based on the weight of stabilised zirconia, preferablyin the range of from 3 to 7% by weight.

Both the catalyst carrier of the downstream and of the upstream part ofthe catalyst system is provided with a catalytically active material,preferably a catalytically active material suitable for the partialoxidation of hydrocarbonaceous feedstocks. Such catalytically activematerials are known in the art. One or more metals selected from GroupVIII of the Periodic Table of the Elements are very suitable ascatalytically active material. Rhodium, iridium, palladium and/orplatinum are preferred, especially rhodium and/or iridium. Typically,the catalyst comprises the catalytically active metal(s) in aconcentration in the range of from 0.02 to 10% by weight, based on thetotal weight of the catalyst, preferably in the range of from 0.1 to 5%by weight. The catalyst may further comprise a performance-enhancinginorganic metal cation selected from Al, Mg, Zr, Ti, La, Hf, Si, Ba, andCe which is present in intimate association supported on or with thecatalytically active metal, preferably a zirconium cation.

The catalyst carrier is provided with the catalytically active materialby means known in the art, e.g. by impregnation or (co)precipitation.

The process according to the present invention is particularlyadvantageous if the catalyst bed of the downstream part of the catalystsystem comprises a fixed arrangement of a metal catalyst carrier. Porousmetal arrangements of such as metal foams, honeycombs or arrangements ofmetal gauze, wire or foil, are very suitable catalyst carriers forcatalytic partial oxidation processes, because they are very resistantto thermal shocks. A disadvantage of metal arrangements, especially ifthey contain thin metal wires, however, is that the metal can melt if itis exposed at high temperatures. It will be appreciated that the meltingtemperature depends inter alia of the metal composition, the form of themetal arrangement and the duration of the exposure to that temperature.In the process according to the present invention, very hightemperatures at the upstream surface of the downstream part of thecatalyst system are avoided such that wire arrangements of metals can beused under severe process conditions as catalyst carrier for thedownstream part.

An advantage of a metal catalyst carrier in the upstream part of thecatalyst system is that it may be provided with means for electricallyheating it, in order to facilitate catalytic ignition of the upstreampart of the catalyst during start-up of the catalyst system. The metalcatalyst carrier of the upstream part may for example be provided withan electrical igniter. Alternatively, the metal upstream part may be inthe form of an igniter. This may for example be realised by using anarrow strip of metal as the catalyst carrier of the upstream part ofthe catalyst system, over which a potential difference can be applied.

In the catalyst system of the process of the present invention, thecatalytic composition of the upstream part and of the downstream partcan be optimised independently from each other. The composition of theupstream part will be optimised towards resistance to high temperaturesand thermal shock, whereas the composition of the downstream part willbe optimised towards maximum degree of conversion and selectivity.

Preferably, the distance between the upstream part and the downstreampart of the catalyst system is small, such that heat losses areminimised, i.e. that a maximum of the heat contained in the effluentfrom the upstream part of the catalyst system is maintained in thereaction zone. A greater distance between the upstream and thedownstream parts of the catalyst system requires a better insulation ofthe reactor against radiative heat losses. The upstream part of thecatalyst system may be arranged on part of the upstream surface of thedownstream part of the catalyst system, provided that the feed mixtureand the feedstock converted at the upstream part can pass the structurein order to contact the downstream part.

The upstream part of the catalyst system may be provided with means fordetermining its temperature, e.g. a resistive temperature sensor in theform of a Pt wire. There is a direct dependency of the temperature ofthe upstream part of the catalyst and the carbon/oxygen ratio in thefeed mixture of catalytic partial oxidation reactions. Thus, such anupstream catalyst with temperature sensor can be advantageously used tocontrol the carbon/oxygen ratio in the feed mixture.

Suitable hydrocarbonaceous feedstocks for the process according to theinvention comprise hydrocarbons, oxygenates or mixtures thereof.Oxygenates are defined as molecules containing apart from carbon andhydrogen atoms at least 1 oxygen atom which is linked to either one ortwo carbon atoms or to a carbon atom and a hydrogen atom. Examples ofsuitable oxygenates are methanol, ethanol, dimethyl ether and the like.The hydrocarbonaceous feedstock is gaseous when contacting the catalyst,but may be liquid under standard temperature and pressure (STP)conditions, i.e. at 0° C. and 1 atmosphere. Preferred hydrocarbonaceousfeedstocks are hydrocarbons. The process according to the presentinvention is especially advantageous if the feedstock is a hydrocarbonstream having an average carbon number of at least 2. Preferably, thefeedstock is a hydrocarbon stream having an average carbon number of atleast 6.

The oxygen-containing gas may be oxygen, air, or oxygen-enriched air,preferably air.

The hydrocarbonaceous feedstock and the oxygen-containing gas arepreferably present in the feed mixture in such amounts as to give anoxygen-to-carbon ratio in the range of from 0.3 to 0.8, more preferablyin the range of from 0.35 to 0.65, even more preferably in the range offrom 0.40 to 0.60. References herein to the oxygen-to-carbon ratio referto the ratio of oxygen in the form of molecules (O₂) to carbon atomspresent in the hydrocarbonaceous feedstock. If oxygenate feedstocks areused, e.g. ethanol, oxygen-to-carbon ratios below 0.3 can suitably beused.

Preferably, the feed mixture additionally comprises steam. If steam ispresent, the steam-to-carbon ratio is preferably in the range of fromabove 0.0 to 3.0, more preferably of from above 0.0 to 1.5, even morepreferably of from above 0.0 to 1.0.

The feed mixture may be contacted with the catalyst at any suitable gashourly space velocity (GHSV). In the process according to the invention,the GHSV will be typically in the range of from 20,000 to 10,000,000Nl/l/h (normal litres of gaseous feed mixture per litre of catalyst perhour), preferably in the range of from 100,000 to 2,000,000 Nl/l/h, morepreferably in the range of from 200,000 to 1,000,000 Nl/l/h. Referenceherein to normal liters is to liters at STP (0° C. and 1 atm.).

The feed mixture may be contacted with the catalyst system at a pressureup to 100 bar (absolute), preferably in the range of from 1 to 50 bar(absolute), more preferably of from 1 to 10 bar (absolute).

The process of this invention could very suitably be used to provide thehydrogen feed for a fuel cell. The conversion of fuel into hydrogen thatis suitable for use in a fuel cell is generally carried out is aso-called fuel processor, comprising a first reaction zone for partiallyoxidising and/or reforming a fuel and a second reaction zone for thewater-gas shift conversion of the effluent of the first reaction zone,optionally followed by a reaction zone for the removal of carbonmonoxide from the effluent of the second reaction zone.

Accordingly, the present invention further relates to a reactorcomprising the catalyst system as hereinbefore defined, the reactorfurther comprising a catalytic reaction zone for the water-gas shiftconversion of the effluent of the downstream part of the catalystsystem.

The reactor according to the invention may optionally comprise areaction zone for the removal of the remaining carbon monoxide from theeffluent of the catalytic reaction zone for the water-gas shiftconversion, preferably a catalytic reaction zone for the selectiveoxidation of carbon monoxide.

According to a further aspect, the present invention relates to a fuelcell system comprising the reactor as hereinbefore defined and a fuelcell. The fuel call may for example be a PEM fuel cell or a solid oxidefuel cell. Such a fuel cell system can for example be applied indomestic system for generating heat and power and in fuel-cell-poweredvehicles. In fuel-cell-powered vehicles, frequent start-ups may occurresulting in exposure of the partial oxidation catalyst to thermalshocks. Since the process and reactor according to the invention isparticularly suitably under thermal shock conditions, the fuel cellsystem according to the invention can advantageously be applied infuel-cell-powered vehicles.

Accordingly, the invention further relates to a vehicle provided with afuel cell system as hereinbefore defined.

The invention will now be illustrated by means of schematic FIGS. 1 to3.

The catalyst system 1 shown in FIG. 1 comprises a hollow cylindricaldownstream part 2 and an upstream part 3. The downstream part 2 is inthe form of a porous arrangement of catalyst carrier in the form ofmetal fibres (fecralloy-type fibres) knitted and pressed in the shape ofa hollow cylinder and provided with Rh and Ir as catalytically activemetals and Zr as modifying cation. The upstream part 3 comprises aresilient fecralloy-type metal foil as catalyst carrier that is providedwith Rh and Ir as catalytically active metals and Zr as modifyingcation. The upstream part 3 is bend in the form of a ring that isarranged on part of the upstream surface 4 of the downstream part 3.

In FIG. 2 is shown part of a reactor containing the catalyst system ofFIG. 1, i.e. the downstream part 2 and the upstream part 3 arranged onpart of its upstream surface 4. The upstream part 3 is contained in theupstream part 5 of the reactor and the downstream part 2 is contained inthe downstream part 6 of the reactor. The reactor further comprises afirst reactant supply conduit 7 for supply of hydrocarbonaceousfeedstock and a second reactant supply conduit 8 for supply ofmolecular-oxygen containing gas and, optionally, steam. During normaloperation of the reactor, the reactants supplied via conduits 7 and 8are mixed in a mixing zone 9, wherein a swirling movement is imposed onthe thus-formed feed mixture. The swirling flow 10 of feed mixture iscontacted with the catalyst system 2, 3. Part of the feed mixture isconverted at the upstream part 3 of the catalyst system and part will beconverted at the downstream part 2. Effluent is discharged via effluentdischarge chamber 11 and discharge conduit 12. The overall direction ofthe fluid flow in the upstream part 5 of the reactor is in dictated witharrow 13. In the downstream part 6 of the reactor, the overall directionof the fluid flow is indicated with arrow 14.

In FIG. 3 is shown part of a reactor tube 15 having an upstream part 5and a downstream part 6. The reactor contains a catalyst system havingan upstream part 2 in the form of a round, metal catalyst carrier plateprovided with Rh and Ir as catalytically active metals and Zr asmodifying cation, and a downstream part 3 in the form of metal fibres(fecralloy-type fibres) knitted and pressed in the shape of a cylinderand provided with Rh and Ir as catalytically active metals and Zr asmodifying cation.

During normal operation of the reactor, a flow of feed mixture 18 isfirst contacted with the metal plate 3 and then with the downstream part2 of the catalyst system. Effluent is discharged in the directionindicated by arrow 19.

The diameter of the metal plate 3 is smaller than the inner diameter ofthe reactor tube 15 such it only partly fills the cross-sectional areaof the fluid flow path and (partly converted) feed mixture can pass thepre-conversion structure in order to be able to contact the upstreamsurface 4 of the downstream part 2 of the catalyst system.

The process according to the invention will be further illustrated bymeans of the following examples. The examples should not be construed tolimit the scope of the invention.

EXAMPLES Example 1 (According to the Invention)

Catalyst System

Downstream Part

A catalyst carrier in the form of a knitted arrangement of commerciallyavailable fecralloy wire (wire diameter 0.2 mm; ex. Resistalloy, UK;wire composition: 72.6% wt Fe, 22% wt Cr, 5.3% wt Al, and 0.1% wt Y),pressed in the shape of a hollow cylinder (outer diameter: 63 mm; innerdiameter: 20 mm; height: 32 mm) was calcined at a temperature of 1050°C. during 48 hours. The calcined wire arrangement was once dipcoated ina commercially available partially-stabilised zirconia (zirconium oxide,type ZO, ex. ZYP Coatings Inc., Oak Ridge, USA). The zirconia ispartially stabilised with 4% wt CaO. After dipcoating, the arrangementwas calcined for 2 hours at 700° C.

The coated arrangement was further provided with 0.7% wt Rh, 0.7% wt Ir,and 2.0% wt Zr, based on the total weight of the downstream part, byimmersing it three times in an aqueous solution comprising rhodiumtrichloride, iridium tetra chloride and zirconyl nitrate. After eachimmersion, the arrangement was dried at 140° C. and calcined for 2 hoursat 700° C.

Upstream Part

A commercially available resilient foil of PM 2000 (ex. PLANSEE,Austria; foil composition: 23.5% wt Fe, 20% wt Cr, 5.5% wt Al, 0.5% wtTi, and 0.5% wt Y) having a length of 60 mm, a height of 15 mm, and athickness of 0.125 mm was calcined at a temperature of 1050° C. during48 hours. The calcined foil was once dipcoated in the samepartially-stabilised zirconia as applied for the downstream part (seeabove). After dipcoating, the foil was calcined for 2 hours at 700° C.The coated foil was further provided with 1.0% wt Rh, 1.0% wt Ir, and2.8% wt Zr, based on the total weight of the coated foil, by immersingit twice in an aqueous solution comprising rhodium trichloride, iridiumtetra chloride and zirconyl nitrate. After each immersion, the foil wasdried at 140° C. and calcined for 2 hours at 700° C.

Catalyst System

The resilient foil 3 is inserted at the inside of the cylindricaldownstream part 2 to form a ring, as shown in FIG. 1, such that part ofthe formed ring covers part of the upstream surface 4, i.e. the surface4 at the inside of the cylinder forming the downstream part 2. The ringis arranged against the upstream surface 4 over a height of 5 mm.

Catalytic Partial Oxidation

The catalyst system as described above is placed in a reactor as shownin FIG. 2. Naphtha (0.74 g/s), air (3.45 g/s), and steam (0.85 g/s) weremixed, pre-heated to a temperature of 190° C. and brought into a swirlmovement. The swirling, pre-heated feed mixture was contacted with thecatalyst system as shown in FIG. 2. The temperature of the upstreamsurface of the cylinder and the temperature of the ring were measured bymeans of an optical pyrometer.

Temperature of the upstream surface of the cylinder (downstream part ofthe catalyst system): 1060° C. Temperature of the ring (upstream part ofthe catalyst system): 1180° C.

Example 2 (Not According to the Invention)

A catalyst system in the form of a hollow cylinder was prepared in thesame way as the downstream part of the catalyst system described inExample 1. The thus-prepared catalyst comprised 0.7% wt Rh, 0.7% wt Ir,and 1.9% wt Zr, based on the total weight of the catalyst. The catalystwas placed in a reactor similar to that shown in FIG. 2, but without anupstream part 3. A catalytic partial oxidation process was performedunder the same conditions as described in Example 1.

Temperature of the upstream surface of the catalyst: 1175° C.

1. A process for the catalytic partial oxidation of a hydrocarbonaceousfeedstock, wherein a feed mixture comprising the hydrocarbonaceousfeedstock and a molecular-oxygen containing gas in such amounts as togive an oxygen-to-carbon ratio in the range of from 0.3 to 0.8 iscontacted with a catalyst system having an upstream part and adownstream part, the downstream part being in the form of a porouscatalyst bed, wherein the catalyst system is retained in a reactor, thereactor comprising an upstream part that contains the upstream part ofthe catalyst system and a downstream part that contains the downstreampart of the catalyst system, wherein the upstream part of the catalystsystem only partly fills the cross-sectional area of the fluid flow pathof the upstream part of the reactor and the downstream part of thecatalyst system completely fills the cross-sectional area of the fluidflow path of the downstream part of the reactor.
 2. The process of claim1, wherein 5% to 75% (v/v) of the feedstock is converted at the upstreampart of the catalyst system.
 3. The process of claim 1, wherein thetemperature of the upstream surface of the downstream part of thecatalyst system is at most 1150° C.
 4. The process of claim 1, whereinthe feed mixture has a swirling movement when contacting the downstreampart of catalyst system.
 5. The process of claim 1, wherein the upstreampart of the catalyst system is in the form of a metal catalyst carrierprovided with a catalytically active material.
 6. The process of claim5, wherein the metal is a high-temperature resistant metal.
 7. Theprocess of claim 5, wherein the metal catalyst carrier of the upstreampart of the catalyst system is in the form of a non-porous metalstructure.
 8. The process of claim 5, wherein the upstream part of thecatalyst system is provided with means for electrically heating it. 9.The process of claim 1, wherein the catalyst bed of the downstream partof the catalyst system comprises a metal catalyst carrier provided witha catalytically active material.
 10. The process of claim 9, wherein themetal catalyst carrier of the catalyst bed of the downstream part of thecatalyst system is an arrangement of metal wire.
 11. The process ofclaim 1, wherein the upstream part of the catalyst system is arranged onpart of the upstream surface of the downstream part of the catalystsystem.
 12. The process of claim 1, wherein the upstream part of thecatalyst system is provided with means for determining its temperature.13. A process for the catalytic partial oxidation of a hydrocarbonaceousfeedstock, wherein a feed mixture comprising the hydrocarbonaceousfeedstock and a molecular-oxygen containing gas in such amounts as togive an oxygen-to-carbon ratio in the range of from 0.3 to 0.8 iscontacted with a catalyst system having an upstream part and adownstream part, the downstream part being in the form of a porouscatalyst bed, wherein the catalyst system is retained in a reactor, thereactor comprising an upstream part that contains the upstream part ofthe catalyst system and a downstream part that contains the downstreampart of the catalyst system, wherein the upstream part of the catalystsystem is in the form of a metal catalyst carrier provided with acatalytically active material and only partly fills the cross-sectionalarea of the fluid flow path of the upstream part of the reactor and thedownstream part of the catalyst system completely fills thecross-sectional area of the fluid flow path of the downstream part ofthe reactor.
 14. The process of claim 13, wherein the metal catalystcarrier of the upstream part of the catalyst system is in the form of anon-porous metal structure.
 15. The process of claim 13, wherein theupstream part of the catalyst system is provided with means forelectrically heating it.
 16. The process of claim 13, wherein thecatalyst bed of the downstream part of the catalyst system comprises ametal catalyst carrier provided with a catalytically active material.17. The process of claim 16, wherein the metal catalyst carrier of thecatalyst bed of the downstream part of the catalyst system is anarrangement of metal wire.
 18. A process for the catalytic partialoxidation of a hydrocarbonaceous feedstock, wherein a feed mixturecomprising the hydrocarbonaceous feedstock and a molecular-oxygencontaining gas in such amounts as to give an oxygen-to-carbon ratio inthe range of from 0.3 to 0.8 is contacted with a catalyst system havingan upstream part and a downstream part, the downstream part being in theform of a porous catalyst bed, wherein the catalyst system is retainedin a reactor, the reactor comprising an upstream part that contains theupstream part of the catalyst system and a downstream part that containsthe downstream part of the catalyst system, wherein the upstream part ofthe catalyst system is in the form of a metal catalyst carrier providedwith a catalytically active material and only partly fills thecross-sectional area of the fluid flow path of the upstream part of thereactor and the downstream part of the catalyst system comprises a metalcatalyst carrier provided with a catalytically active material andcompletely fills the cross-sectional area of the fluid flow path of thedownstream part of the reactor.